(Trying again in plain text and without the 100KiB log file.) Hi linux-btrfs,
The context of these three questions is that I'm experiencing occasional hangs for several seconds while btrfs-transacti works, and very long boot times. General comments welcome. System info at bottom, end part of dmesg.log attached. Q1: I keep a lot of read-only snapshots (> 300 total) of all of my subvolumes and haven't deleted any so far. Is this in itself a problem or unanticipated use of btrfs? Q2: I have some files that remain heavily fragmented (according to filefrag) even after I run btrfs fi defragment. I think this happens because btrfs doesn't want to unlink parts of the files from their snapshotted copies. Can I tell btrfs to defragment them anyway, and not worry about wasting space? And can I make the autodefrag mount option do this? For example (not all output shown): # filefrag * ... system@1973a03e3af1449ba5dd93362953fd5f-0000000000000001-00051f9377f11af6.journal: 553 extents found ... # btrfs fi defragment -rf . # filefrag * ... system@1973a03e3af1449ba5dd93362953fd5f-0000000000000001-00051f9377f11af6.journal: 331 extents found ... Q3: What's the best way to tell which files are causing the hangs? My current method is to make an educated guess (e.g. think of programs that store large database files) then use filefrag to see if there's fragmentation. I'm not confident I've found all the sources of bad performance. Thanks, James System info: [root@angel-nixos:~]# uname -a Linux angel-nixos 3.18.20 #1-NixOS SMP Thu Jan 1 00:00:01 UTC 1970 x86_64 GNU/Linux [root@angel-nixos:~]# btrfs --version btrfs-progs v4.2 [root@angel-nixos:~]# btrfs fi show Label: 'AngelBtrfs' uuid: 7f4b4b5d-1ba5-46cc-b782-938e3600a427 Total devices 2 FS bytes used 1.06TiB devid 5 size 2.00TiB used 1.07TiB path /dev/mapper/KfricBtrSec devid 6 size 2.00TiB used 1.07TiB path /dev/mapper/SfricBtrSec btrfs-progs v4.2 [root@angel-nixos:~]# btrfs fi df / Data, RAID1: total=1.01TiB, used=1.01TiB System, RAID1: total=32.00MiB, used=192.00KiB Metadata, RAID1: total=60.00GiB, used=58.65GiB GlobalReserve, single: total=512.00MiB, used=0.00B
end_of_dmesg.log
Description: Binary data